My reference to the 0.2 to 0.4 ppm FC was from the article you linked to. So I'm glad you agree that it isn't particularly feasible for higher bather loads. That's where CYA becomes very useful as it holds chlorine in reserve releasing it as needed while keeping the active concentration at a lower level that slows down disinfection by-product formation. The reason no one seems to think of it this way in spite of the clear science known since at least 1974 is that the chlorinated cyanurate industry only talks about CYA protecting chlorine from sunlight. You really should read the introductory sections in the paper in this link. You see, if the industry started to talk about how low it makes the active chlorine concentration, then someone might ask if this affects algae growth and then someone would realize that continued use of stabilized chlorine products raises the CYA letting algae grow if you don't proportionately raise the FC. That is, the product (e.g. Trichlor and Dichlor) has a built-in obsolescence requiring use of algaecides or phosphate removers in many cases.

As you point out, ozone is a strong oxidizer and will oxidize chemicals that chlorine won't or that chlorine simply combines with (i.e. combined chlorines). This isn't helpful in the bulk pool water where monochloramine will still form quickly and it isn't particularly necessary with the normal oxidation of ammonia since that is still mostly complete before even one turnover, but it is very useful for persistent combined chlorines or for organic substances that more slowly combine with chlorine. Also as you point out, you have to have a powerful enough ozonator for a pool -- most residential units aren't strong enough. Ozone can oxidize chlorine to chlorate so you are right that the conditions should be such to minimize that -- I'm not familiar with which conditions are best for that. I suspect that using ozone in a light bather load pool may end up using more chlorine while in a heavier bather load pool it may lower chlorine use -- the difference being whether the ozone can eliminate bather waste quickly enough so with higher concentrations of bather waste from higher bather load that's more likely.

As for combined chlorine and the 10x rule, it's wrong. The 10x rule came from the stoichiometry of chlorine oxidizing ammonia, not chlorine oxidizing combined chlorine (such as monochloramine). It takes 3 chlorine molecules to combine with 2 ammonia molecules to fully oxidize them to nitrogen gas (and hydrochloric acid). That's a ratio of 1.5. When you convert the units to ppm for each compound, where by convention chlorine is measured as ppm Cl2 (chlorine gas) equivalent while ammonia is measured as ppm N (atomic nitrogen) equivalent, then you get a ratio of 7.5. Due to some side reactions, the reaction gets to completion with a ratio of 8 to 10 chlorine to 1 ammonia. This is where the 10x came from. However, Combined Chlorine (CC), such as monochloramine, is not measured in ammonia units, but in chlorine units as the test is essentially a chlorine test. Also, of the 3 chlorine to 2 ammonia, two of the chlorine are already combined with two ammonia to form two monochloramine. It technically takes only 0.5 times the amount of measured CC to oxidize it, though taking into account side reactions it's slightly higher, but using a rule of at least having an FC that is equal to the CC is sufficient.

The above discussion regarding the 10x rule is with regards to stoichiometry, so having enough chlorine to not run out. It is not about reaction rates so having a higher FC will make any chlorine reactions go faster. So your rule of raising the FC until your CC level is lower relates to this reaction effect, but technically it's not the FC alone that matters but the FC/CYA ratio if CYA is present because reaction rates are based on the active chlorine (hypochlorous acid) concentration and not on FC which mostly measures the chlorine reserve (chlorine attached to CYA as chlorinated cyanurates).

If one has an FC/CYA ratio of 10% or more, then one has oxidation of ammonia in a matter of hours in pools. If the bather load is higher, then a higher FC/CYA ratio of 20% would speed up the oxidation to hopefully keep up with the bather waste introduction rate. Unfortunately, though ammonia oxidation is well understood, the oxidation of urea is not and urea is by far the largest component of sweat and urine. Since urea oxidation is slower, it will build up until you get to a steady state of bather waste introduction vs. oxidation by chlorine. Again, this is where the ozone can be very helpful as a supplemental oxidizer.

Richard, this article you pointed out is extremely telling. Below are some quotes which I tried to verify on the official Pristine Blue website. It seems their forum has been inactive for months and is now home to spammers. There is no claim that PB is a chlorine alternative and they prefer to call it a "non-chlorine" product.

Is chlorine in deep water?Chemistry & Industry â€” 21 August 2006 wrote:... But what is not clear is whether PB can be relied upon as a stand-alone sanitiser and whether it controls viruses.

PB is approved as an algaecide in the US, and is used in more than 600,000 private US pools. It is marketed in Europe by Pristine Pools Limited (PPL) and was launched in the UK and France earlier this year (2006).

One reason for the uncertainty over its value as a stand-alone sanitiser is the apparent inconsistenciesbetween information issued by PPL (Pristine Pools Limited, UK) to pool users in Europe and that given by Earth Science Laboratories (ESL), when marketing it as Earthtec to US drinking water suppliers. PPL promotes PB as a â€˜chlorine-free alternativeâ€™. But ESL says that Earthtec, which shares PBâ€™s EPA registration number â€” 64962 â€” â€˜enhances the efficiency of chlorineâ€™.....Doubts about the suitability of PB as a bactericide were further reinforced when in June, the New York State pesticide database said PB/Earthtec could be used in hot tubs, spas, swimming pools and potable water but only as an algaecide.

I tried to access the official EU distributors website (pristineblue.co.uk) but the site no longer exists and returns a message of *** This registration has been SUSPENDED. ***! I'll try to get some local feedback, but I have this uneasy feeling about PB all of a sudden.

Early morning on a poorly lit laptop in motel room drinking my first coffee so i can hardly read LOL. Richard, as usual your post has tons of info in it. 2 things though. That article refers to German Din standard and their numbers refer to a pool that has had 100% of the water heavily Ozonated and chlorinated and then de-ozonated and de-chlorinated. Then pretty much trace amounts of both are added to the return water. I think they test for Ozone 4" off the water and allow up to .4ppm.

But of course I have not read the standard in a long time either so i should say I think they used to do this. Good idea though and worked well. We seem to think we have so much water over here we can still throw it away.

chem geek wrote:There are only 3 EPA DIS/TSS-12 approved disinfectants: chlorine, bromine and biguanide/PHMB/Baqua. In addition, it appears that silver ion used in conjunction with higher levels of non-chlorine shock (monopersulfate, MPS) are approved, but only at high spa temperatures (i.e. not for pools).

I looked for the documentation on these chemicals at the EPA site but was only able to find the DIS/TSS-12 standard and not which chemicals it has been awarded to.

This link is an example of the consequences of claiming to be a disinfectant (as opposed to simply using a chemical that is registered pesticide).

You can use this link to search the pesticides database. Earth Science Laboratories, Inc. that makes PristineBlue has firm number 64962. You can use this link to search for specific product registrations. This page lists the registrations for that company. Good luck in finding PristineBlue in that list -- if you know the EPA registration number, then that can help. They could just be riding on the use of copper sulfate which is generally registered as a pesticide (algaecide, not disinfectant).

To be continued on the next post since there is a limit of 5 URLs per post...

This link lets you look up info on any of the registered pesticide chemicals. This link is for copper sulfate and note that the word "disinfectant" is not listed and that for water uses it is an algaecide only, not a disinfectant. Now look at this link for calcium and sodium hypochlorite and notice that it IS a disinfectant and used for swimming pools and spas, among other things. Bromine is described as a disinfectant here. PHMB (biguanide/Baqua) is described here.

To be continued on the next post since there is a limit of 5 URLs per post...

I don't have time to go through the entire long list and unfortunately I could not find an explicit list of DIS/TSS-12 items. There aren't that many "alternatives" so its easier to just look them up such as copper that I did above or silver here though silver does kill bacteria faster than copper (though copper is better against algae) and is mentioned as a disinfectant for pools, BUT...

This link is a response from the EPA referring to Zodiac Pool Care (makers of Nature2) where the Zodiac Nature product that uses silver and copper was claiming to kill bacteria and the EPA keeps telling them over and over again that their product can only claim the product is effective when used with a registered chlorine product. This is specifically in regard to DIS/TSS-12. Read the document's "VI. Conclusions and Recommendations" section carefully. Silver and copper alone do not kill bacteria quickly enough to be used alone as a swimming pool disinfectant. The only allowed claim is an an algaecide, though that is shown in the other links I gave above (i.e. this document doesn't say that explicitly). This link is another mineral product with silver (not copper) that requires at least 0.5 ppm chlorine to be used with it.

Now remember that DIS/TSS-12 has a laboratory test that is extraordinarily difficult to pass. In fact, if the test were done properly with Cyanuric Acid (CYA) in the water, then even chlorine products would not pass this test -- as little as 5 ppm CYA would cause chlorine products (at 1 ppm FC) not to pass. Instead of a 99.9999% (6-log) kill in less than 30 seconds, a more reasonable limit would be something like 99% (2-log) in around 1 minute (or less) since that is still very likely to prevent person-to-person transmission of pathogens (bacteria and viruses). For 99% kill of Stretococcus faecalis, with 3 ppm FC with 30 ppm CYA (technically, an FC that is roughly 10% of the CYA level) it takes less than a minute while with 1 ppm FC and 100 ppm CYA (the current extreme limit in most standards) it takes between 4-9 minutes (see this link). Silver would have a kill rate that might be in that 10-20 minute range, but copper would be slower -- though both would kill 50% faster than bacteria reproduce (which is roughly 15-60 minutes generation rate) except they don't inactivate viruses very effectively. Therefore, mineral ion systems can be seen as an insurance policy to prevent uncontrolled bacteria growth, but should not be seen as fast-acting sanitizers since they most likely do not kill fast enough to prevent person-to-person transmission.

To be continued on the next post since there is a limit of 5 URLs per post...

The only exception to the 3 EPA-approved sanitizers that I am aware of is the use of silver with non-chlorine shock (potassium monopersulfate, MPS) at hot water temperatures in hot tubs. This link is to the EPA registration info on Nature2 when used with MPS. This post of mine on another forum talks about how technically this may work.

In this post on another forum I list hot tub rash/itch/lung incidents in an attempt to roughly determine the cause, though clearly it's very anecdotal and not scientific. It looks like the lack of a fast-acting sanitizer is the primary reason and that using a mineral ion system (i.e. silver and/or copper) reduces but does not eliminate the risk. I would guess that if you use a mineral ion system and don't use a fast-acting sanitizer during or after a soak, then bacteria shed from your body can form biofilms before getting killed and then they are resistant to subsequent attack even if chlorine is then used. There also seemed to be a risk when using Dichlor-only for more than a month or two and that's most likely due to the buildup of Cyanuric Acid (CYA) since for every 10 ppm Free Chlorine (FC) added by Dichlor, it also increases CYA by 9 ppm.

In this post on this forum, I give some more details about copper kill times.

I would like to say a few things regarding mineral products versus chlorine which kills many harmful water-borne contaminates, parasites and disease-causing pathogens that would otherwise make us sick. The EPA requires a concentration of 0.2 ppm (parts per million) of chlorine in all tap water in the United States, with the average being closer to 4 ppm.

Of course there is a price to pay for disinfecting our water, chlorine is responsible for many harmful affects. It's same harsh nature that allows it to kill the bad things in our water has the same effect on our hair and skin. Attacking our cells like the poison that it is. More importantly, it binds to organic material in the water to create something called disinfection byproducts (DBP). These byproducts have been linked to birth defects and cancer and count in the thousands of different types of compounds. Chloroform is a known toxin that is a trihalomethane (THM), a type of DBP that is linked to liver and kidney cancer, as well as miscarriages and birth defects. Now, water treatment professionals are constantly detecting, tracking and monitoring these DBP's in our water supply and looking for ways to reduce them. Bathing in a hot tub filled with chlorine enters your body 2 ways, through your skin and through breathing.

I agree that with most mineral systems, kill rates are slower but I'd rather take my chances soaking in minerals than I would chlorinated water. I am involved with Humanitarian groups and have been involved with a company that has been in research, development and patent work for years with the goal of creating the first mineral sanitizer. We have used their product in third world countries to help combat water born diseases. Their problem was not attaining kill rates and log reductions necessary to get EPA approval as a sanitizer, they have those. It was getting through the politics that are involved with big businesses and the EPA. I along with others have used their product to help combat water born diseases in 3rd world countries with unbelievable results. I along with the former head (retried) of water quality for the state health department use their product in our hot tubs. I have found it to be the easiest and best product I have ever used. It is a copper/silver/organic formula, which is patented, so it is unlike any other product I have seen.

The product has multiple complexants which inhibit calcium, iron, rust and scale buildup and it has a pH anchor incorporated all into one product. I've been telling them to sell their product to hot tub users directly to help fund their humanitarian efforts. Dealer's won't want to carry it because it is too cost effective and eliminates the need to buy a multitude of other products. There product eliminates the need to buy and add multiple products which are expensive and most people find too hard to balance. I was a manufacturer of Aquatic exercise pools, have been a hot tub dealer, pool builder and have been in and out of the pool and spa industry for almost 20 years so I am very familiar with most of the products that are being used.

Now back to chlorine, most commercial pools across the country have the same common problems, one being high pH ... typically they are in a range of 8 and above when tested. What this does, is cause chlorine to at 8 ph levels chlorine has become 80% less effective in killing pathogens. At 8.5 ph the chlorine has lost 95% of its effectiveness.

So what does this mean? If you have high pH in your hot tub, your chlorine is not working well enough to kill bacteria and viruses and we are poisoning our bodies while soaking in a toxic bath of chemicals. With minerals and in conjunction with small does of chlorine I have never had any issues contracting bacterial infections and I have used one product for the past 10 years. Unfortunately it is not available yet. I am trying to convince the manufacturer to distribute their product in the hot tub industry ... I love it when we read what all of these so called experts state on blogs telling us that we should be using chlorine due to it being an EPA approved product.I find that almost comical, if you call your local health officials and speak to them regarding water quality, you will find out the people who test the public facilities typically won't let their own children use them, do you know why? ... ask them and you will get the same answer ... HIGH CHLORINE LEVELS and HIGH PH LEVELS, that pose a health risk due to lack of sanitation. When they do have the PH levels balanced the Chlorine levels are too high ... they know that the toxicity of those bodies of water are more likely to be unsafe than safe or they won't take the risk of letting their own children swim in them ...read about the dangers chlorine poses to swimmers ...http://swimming.about.com/od/allergyand ... roblem.htm

The University of Arizona did a test and recommends dual sanitation using minerals with Chlorine, here's their report on the the advantages of using a dual stage method of sanitationhttp://algaebar.com/algaebar/report.html